There is probably a really obvious solution to this - maybe I've pressed too many buttons... First few times I got the camera out it was great but today when I switch on my D40 all seems well, auto focus ok but if I press the shutter (in auto or other mode) I hear the shutter move but then see Err in the viewfinder and get a 'press the shutter again' message on the LCD , I do and this returns the shutter but no image recorded. Is this me or the camera or both?